Many large data storage systems such as the IBM 3390 storage system or other compatible systems employ two primary types of controller boards to interface one or more host computers with a plurality of direct access storage devices such as disk drives. The two controllers include a channel adapter, which serves as an interface between the disk storage system and one or more host computers, and a disk adapter which interfaces with one or more data storage devices such as disk drives. The channel adapter receives data and commands over one or more bi-directional channels from the host, and transmits data as well as storage system status information to the host whereas the disk adapter transfers data between the data storage system, cache memory, and the data storage devices.
Although each of these controller boards can be manufactured with little waste of hardware real estate or power consumption to achieve their specific function, each board is thus able to function only as one of the two required controller boards.
There are several negative features, however, of implementing only one function per controller board. These include the cost to the system user of stocking two different kinds of spare controller boards, as well as the manufacturing problems resulting from the requirement to produce, test and inventory two different controller boards. Thus, manufacturing costs as well as the costs of data storage system ownership could be drastically reduced with a single, multi-function controller board.